Purification,cloning, and properties of an acyltransferase controlling shikimate and quinate ester intermediates in phenylpropanoid metabolism

A protein hydrolyzing hydroxycinnamoyl-CoA esters has been purified from tobacco stem extracts by a series of high pressure liquid chromatography steps. The determination of its N-terminal amino acid sequence allowed design of primers permitting the corresponding cDNA to be cloned by PCR. Sequence analysis revealed that the tobacco gene belongs to a plant acyltransferase gene family, the members of which have various functions. The tobacco cDNA was expressed in bacterial cells as a recombinant protein fused to glutathione S-transferase. The fusion protein was affinity-purified and cleaved to yield the recombinant enzyme for use in the study of catalytic properties. The enzyme catalyzed the synthesis of shikimate and quinate esters shown recently to be substrates of the cytochrome P450 3-hydroxylase involved in phenylpropanoid biosynthesis. The enzyme has been named hydroxycinnamoyl-CoA: shikimate/quinate hydroxycinnamoyltransferase. We show that p-coumaroyl-CoA and caffeoyl-CoA are the best acyl group donors and that the acyl group is transferred more efficiently to shikimate than to quinate. The enzyme also catalyzed the reverse reaction, i.e. the formation of caffeoyl-CoA from chlorogenate (5-O-caffeoyl quinate ester). Thus, hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyltransferase appears to control the biosynthesis and turnover of major plant phenolic compounds such as lignin and chlorogenic acid.     

Hydroxycinnamoyltransferases Involved in the Accumulation of Caffeic Acid Esters in Gametophytes and Sporophytes of Equisetum arvense

Four hydroxycinnamoyltransferases from Equisetum arvense L. were studied that catalyze the formation of mono-O-caffeoyl-meso-tartrate, di-O-caffeoyl-meso-tartrate, 5-O-caffeoylshikimate (dactylifrate), and 5-O-caffeoylquinate (chlorogenate). The enzymes were classified as coenzyme A (CoA)-ester-dependent acyltransferases (EC 2.3.1), i.e. hydroxycinnamoyl-CoA:meso-tartrate hydroxycinnamoyltransferase (CTT), hydroxycinnamoyl-CoA:caf-feoyl-meso-tartrate hydroxycinnamoyltransferase (CCT), hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (CST), and hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferase. The CTT, CCT, and CST were partially purified and separated from E. arvense gametophytes by hydrophobic interaction chromatography on Fractogel TSK Butyl-650 followed by molecular exclusion on fast protein liquid chromatography-Superdex-75 with 87-, 62-, and 130- fold enrichments and 12, 8, and 11% yields, respectively. The enzyme activities obtained with caffeoyl-CoA were 95 (CTT), 74 (CCT), and 200 [mu]kat (CST) kg-1 protein. The apparent native relative molecular weight values were found to be approximately 45,000 (CTT), 52,000 (CCT), and 50,000 (CST). Each enzyme showed highest activities at pH 7.5, the CCT and CST in Tris-HCl (1.2 and 1.0 M) and the CTT in imidazole-HCl (1.25 M). Enzyme activities were stimulated more than 3-fold by 100 mM ascorbate. The apparent energies of activation (kilojoules mol-1) were calculated to be 56 (CTT), 69 (CST), and 76 (CCT). The enzymes accepted cinnamoyl-CoA and various hydroxycinnamoyl-CoAs. The time course of the transferase activities along with that of a fourth one, hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferase, and the pattern of product accumulation were determined during a 1-year growth period of the E. arvense sporophytes.     

The role of quinate and shikimate in the metabolism of lactobacilli

The metabolism of (–)-quinate and shikimate by one heterofermentative strain,actobacillus pastorianus, and by one homofermentative strain,Lactobacillus plantarum, has been studied using growing and washed cells. Both organisms reduced quinate and shikimate under anaerobic conditions in the presence of suitable hydrogen donors including fructose, glucose andd(–) andl(+)-lactates. The end-product ofL.pastorianus metabolism was dihydroshikimate butL.plantarum carried the reduction a stage further tocis-3,4-dihydroxycyclohexanecarboxylate and formed, simultaneously, catechol. The enzymes involved in these reductions are induced; their importance in the metabolism of lactobacilli is discussed.     

Chorismate‐dependent transcriptional regulation of quinate/shikimate utilization genes by LysR‐type transcriptional regulator QsuR in Corynebacterium glutamicum: carbon flow control at metabolic branch point

The qsu operon of Corynebacterium glutamicum comprises four genes (qsuABCD) that underpin the microorganism's quinate/shikimate utilization pathways. The genes encode enzymes that catalyse reactions at the metabolic branch point between the biosynthesis route for synthesis of aromatic compounds and the catabolic route for degradation of quinate and shikimate for energy production. A qsuR gene located immediately upstream of qsuA encodes a protein (QsuR) which activates the operon in the presence of quinate or shikimate. Three observations support chorismate, an intermediate of the biosynthesis route, as a direct effector of QsuR: First, induction of qsuA mRNA in the presence of either quinate or shikimate disappears upon deletion of the gene encoding chorismate synthase. Second, chorismate accumulates when the operon is induced. Third, a DNase I‐protected segment by QsuR is shortened in the presence of chorismate. The QsuR tetramer senses the accumulation of chorismate and activates qsu genes that promote the quinate/shikimate catabolic instead of the aromatic compounds biosynthetic route. Such chorismate‐dependent control of carbon flow has not been previously described.     

Enzymic synthesis of caffeoylglucaric Acid from chlorogenic Acid and glucaric Acid by a protein preparation from tomato cotyledons

The phenylpropane metabolism of tomato (Lycopersicon esculentum Mill) cotyledons was investigated. The HPLC analysis revealed two hydroxycinnamic-acid conjugates as major components, identified as chlorogenic acid (5-O-caffeoylquinic acid) and caffeoylglucaric acid (2-O- or 5-O-caffeoyl-glucaric acid). Quantitative analyses indicated a precursor-product relationship between the chlorogenic and caffeoylglucaric acids. Protein preparations from tomato cotyledons were found to catalyze the formation of caffeoylglucaric acid with chlorogenic acid as acyl donor and free glucaric acid as acceptor molecule. This enzyme activity, possibly to be classified as hydroxycinnamoylquinic acid:glucaric acid hydroxycinnamoyltransferase, acts together with hydroxycinnamoyl-CoA: quinic acid hydroxycinnamoyltransferase.     

Discovery of nigerose phosphorylase from Clostridium phytofermentans

A novel phosphorylase from Clostridium phytofermentans belonging to the glycoside hydrolase family (GH) 65 (Cphy1874) was characterized. The recombinant Cphy1874 protein produced in Escherichia coli showed phosphorolytic activity on nigerose in the presence of inorganic phosphate, resulting in the release of d-glucose and β-d-glucose 1-phosphate (β-G1P) with the inversion of the anomeric configuration. Kinetic parameters of the phosphorolytic activity on nigerose were k _cat = 67 s⁻¹ and K _m = 1.7 mM. This enzyme did not phosphorolyze substrates for the typical GH65 enzymes such as trehalose, maltose, and trehalose 6-phosphate except for a weak phosphorolytic activity on kojibiose. It showed the highest reverse phosphorolytic activity in the reverse reaction using d-glucose as the acceptor and β-G1P as the donor, and the product was mostly nigerose at the early stage of the reaction. The enzyme also showed reverse phosphorolytic activity, in a decreasing order, on d-xylose, 1,5-anhydro-d-glucitol, d-galactose, and methyl-α-d-glucoside. All major products were α-1,3-glucosyl disaccharides, although the reaction with d-xylose and methyl-α-d-glucoside produced significant amounts of α-1,2-glucosides as by-products. We propose 3-α-d-glucosyl-d-glucose:phosphate β-d-glucosyltransferase as the systematic name and nigerose phosphorylase as the short name for this Cphy1874 protein.     

Structurally diverse dehydroshikimate dehydratase variants participate in microbial quinate catabolism

Quinate and shikimate can be degraded by a number of microbes. Dehydroshikimate dehydratases (DSDs) play a central role in this process, catalyzing the conversion of 3‐dehydroshikimate to protocatechuate, a common intermediate of aromatic degradation pathways. DSDs have applications in metabolic engineering for the production of valuable protocatechuate‐derived molecules. Although a number of Gram‐negative bacteria are known to catabolize quinate and shikimate, only limited information exists on the quinate/shikimate catabolic enzymes found in these organisms. Here, we have functionally and structurally characterized a putative DSD designated QuiC1, which is present in some pseudomonads. The QuiC1 protein is not related by sequence with previously identified DSDs from the Gram‐negative genus, Acinetobacter, but instead shows limited sequence identity in its N‐terminal half with fungal DSDs. Analysis of a Pseudomonas aeruginosa quiC1 gene knock‐out demonstrates that it is important for growth on either quinate or shikimate. The structure of a QuiC1 enzyme from P. putida reveals that the protein is a fusion of two distinct modules: an N‐terminal sugar phosphate isomerase‐like domain associated with DSD activity and a novel C‐terminal hydroxyphenylpyruvate dioxygenase‐like domain. The results of this study highlight the considerable diversity of enzymes that participate in quinate/shikimate catabolism in different microbes.     

Conversion of Quinate to 3-Dehydroshikimate by Ca-Alginate-Immobilized Membrane of Gluconobacter oxydans IFO 3244 and Subsequent Asymmetric Reduction of 3-Dehydroshikimate to Shikimate by Immobilized Cytoplasmic NADP-Shikimate Dehydrogenase

The membrane fraction of Gluconobacter oxydans IFO 3244, involving membrane-bound quinoprotein quinate dehydrogenase and 3-dehydroquinate dehydratase, was immobilized into Ca-alginate beads. The Ca-alginate-immobilized bacterial membrane catalyzed a sequential reaction of quinate oxidation to 3-dehydroquinate and its spontaneous conversion to 3-dehydroshikimate under neutral pH. An almost 100% conversion rate from quinate to 3-dehydroshikimate was observed. NADP-Dependent cytoplasmic enzymes from the same organism, shikimate dehydrogenase and D-glucose dehydrogenase, were immobilized together with different carriers as an asymmetric reduction system forming shikimate from 3-dehydroshikimate. Blue Dextran 2000, Blue Dextran-Sepharose-4B, DEAE-Sephadex A-50, DEAE-cellulose, and hydroxyapatite were effective carriers of the two cytoplasmic enzymes, and the 3-dehydroshikimate initially added was converted to shikimate at 100% yield. The two cytoplasmic enzymes showed strong affinity to Blue Dextran 2000 and formed a soluble form of immobilized catalyst having the same catalytic efficiency as that of the free enzymes. This paper may be the first one on successful immobilization of NAD(P)-dependent dehydrogenases.     

Eryngase: a Pleurotus eryngii aminopeptidase exhibiting peptide bond formation activity

An aminopeptidase that has peptide bond formation activity was identified in the cell-free extract of carpophore of Pleurotus eryngii. The enzyme, redesignated as eryngase, was purified for homogeneity and characterized. Eryngase had a molecular mass of approximately 79 kDa. It showed somewhat high stability with respect to temperature and pH; it was inhibited by iodoacetate. Among hydrolytic activities toward aminoacyl-p-nitroanilides (aminoacyl-pNAs), eryngase mainly hydrolyzed hydrophobic l-aminoacyl-pNAs and exhibited little activity toward d-Ala-pNA and d-Leu-pNA. In terms of peptide bond formation activity, eryngase used various aminoacyl derivatives as acyl donors and acceptors. The products were all dipeptidyl derivatives. Investigation of time dependence on peptide synthesis revealed that some peptides that are not recognized as substrates for hydrolytic activity of eryngase could become good targets for synthesis. Furthermore, eryngase has produced opioid dipeptides––l-kyotorphin (l-Tyr-l-Arg) and d-kyotorphin (l-Tyr-d-Arg)––using l-Tyr-NH₂ and d- and l-Arg-methyl ester respectively as an acyl donor and acceptor. Yield evaluation of kyotorphin synthesis indicated that the conversion ratio of substrate to kyotorphin was moderate: the value was estimated as greater than 20%.     

Hydroxycinnamoyl-CoA:Putrescine Hydroxycinnamoyltransferase in Tobacco Cell Cultures with High and Low Levels of Caffeoylputrescine

A new hydroxycinnamoyl-CoA:putrescine hydroxycinnamoyltransferase (PHT) was detected in two variant lines of Nicotiana tabacum L. (TX1, TX4) accumulating markedly different levels of caffeoylputrescine. The enzyme accepted only the aliphatic diamines putrescine, cadaverine and 1,3-diaminopropane at a ratio of 100:33:8. Caffeoyl- and feruloyl-CoAs were the best acyl donors. The apparent K_m-values for caffeoyl-CoA and putrescine were near 3 and 10 micromolar, respectively, at the pH-optimum of 10.0. PHT activity was quite similar in low producing TX1 and high producing TX4 cells, while some other biosynthetic enzymes (phenylalanine ammonia-lyase, ornithine decarboxylase) were greatly enhanced in TX4 cells, suggesting that PHT does not catalyze the rate-limiting step in hydroxycinnamoylputrescine formation.     

Export,purification, and activities of affinity tagged <Emphasis Type="Italic">Lactobacillus reuteri</Emphasis> levansucrase produced by <Emphasis Type="Italic">Bacillus megaterium</Emphasis>

Fructosyltransferases, like the Lactobacillus reteri levansucrase, are important for the production of new fructosyloligosaccharides. Various His₆- and Strep-tagged variants of this enzyme were recombinantly produced and exported into the growth medium using the Gram-positive bacterium Bacillus megaterium. Nutrient-rich growth medium significantly enhanced levansucrase production and export. The B. megaterium signal peptide of the extracellular esterase LipA mediated better levansucrase export compared to the one of the penicillin amidase Pac. The combination of protein export via the LipA signal peptide with the coexpression of the signal peptidase gene sipM further increased the levansucrase secretion. Fused affinity tags allowed the efficient one-step purification of the recombinant proteins from the growth medium. However, fused peptide tags led to slightly decreased secretion of tested fusion proteins. After upscaling 2 to 3 mg affinity tagged levansucrase per liter culture medium was produced and exported. Up to 1 mg of His₆-tagged and 0.7 mg of Strep-tagged levansucrase per liter were recovered by affinity chromatography. Finally, the purified levansucrase was shown to synthesize new fructosyloligosaccharides from the novel donor substrates d-Gal-Fru, d-Xyl-Fru, d-Man-Fru, and d-Fuc-Fru. R. Biedendieck and R. Beine contributed equally to this work.     

Hydroaromatic metabolism in Rhodococcus rhodochrous: purification and characterisation of its NAD-dependent quinate dehydrogenase

Quinate grown cells of Rhodococcus rhodochrous N75 metabolized both quinate and shikimate via protocatechuate to succinate and acetyl CoA. The initial enzyme of the hydroaromatic pathway, quinate dehydrogenase was purified 188-fold to electrophoretic homogeneity. The enzyme is a monomer with a native relative molecular mass of 44,000 and is NAD-dependent. The enzyme is highly stereospecific with regard to hydroaromatic substrates, oxidising only the axial hydroxyl group at C-3 of (-)-isomers of quinate, shikimate, dihydroshikimate and t-3,t-4-dihydroxycyclohexane-c-1-carboxylate, but shows activity with several NAD analogues.     

Evolution of structure and substrate specificity ind-alanine:d-Alanine ligases and related enzymes

Thed-alanine:d-alanine-ligase-related enzymes can have three preferential substrate specificities. Usually, these enzymes synthesized-alanyl-d-alanine. In vancomycin-resistant Gram-positive bacteria, structurally related enzymes synthesized-alanyl-d-lactate or Dalanyl-d-serine. The sequence of internal fragments of eight structurald-alanine:d-alanine ligase genes from enterococci has been determined. Alignment of the deduced amino acid sequences with those of other related enzymes from Gram-negative and Gram-positive bacteria revealed the presence of four distinct sequence patterns in the putative substrate-binding sites, each correlating with specificity to a particular substrate (d-alanine:d-lactate ligases exhibited two patterns). Phylogenetic analysis showed different clusters. The enterococcal subtree was largely superimposable on that derived from 16S rRNA sequences. In lactic acid bacteria, structural divergence due to differences in substrate specificity was observed. Glycopeptide resistance proteins VanA and VanB, the VanC-type ligases, and Dd1A and DdlB from enteric bacteria andHaemophilus influenzae constituted separate clusters. Correspondence to: P. Courvalin     

Purification of hydroxycinnamoyl-CoA:tyramine hydroxycinnamoyltransferase from cell-suspension cultures of Solanum tuberosum L. cv. Datura

A pathogen-elicitor-inducible acyltransferase [tyramine hydroxycinnamoyltransferase (THT); EC 2.3.1], which catalyzes the transfer of hydroxycinnamic acids from hydroxycinnamoyl-CoA esters to tyramine in the formation of N-hydroxycinnamoyltyramine, was purified to apparent homogeneity from cell-suspension cultures of potato (Solanum tuberosum L. cv. Datura), with a 1400-fold enrichment, a 5% recovery and a final specific activity of 208 mkat·(kg protein)^–1. Affinity chromatography on Reactive Yellow-3-Agarose using the acyl donor (feruloyl-CoA) as eluent was the decisive step in the purification sequence. The purified protein showed a native molecular mass of ca. 49 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence and in the absence of a reducing agent (2-mercaptoethanol) indicated that THT is a heterodimer in which the protein subunits (ca. 25 kDa) are non-covalently associated. The enzyme was stimulated fivefold by 10 mM Ca²⁺. The apparent K _m value for tyramine was dependent on the nature of the hydroxycinnamoyl-CoA present. Thus, the K _m value for tyramine was about tenfold greater (174 M) in the presence of 4-coumaroyl-CoA than in the presence of feruloyl-CoA (20 M).Abbreviations PAL phenylalanine ammonia-lyase - THT hydroxycinnamoyl-CoA:tyramine hydroxycinnamoyltransferase We thank the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for financial support. Further support by a grant from the Studienstiftung des Deutschen Volkes to H.H. is gratefully acknowledged.     

Molecular characterization and heterologous expression of quinate dehydrogenase gene from <Emphasis Type="Italic">Gluconobacter oxydans</Emphasis> IFO3244

The quinate dehydrogenase (QDH) from Gluconobacter oxydans IFO3244 exhibits high affinity for quinate, suggesting its application in shikimate production. Nucleotide sequence analysis of the qdh gene revealed a full-length of 2475-bp encoding an 824-amino acid protein. The qdh gene has the unusual TTG translation initiation codon. Conserved regions and a signature sequence for the quinoprotein family were observed. Phylogenetic analysis demonstrated relatedness of QDH from G. oxydans to other quinate/shikimate dehydrogenases with the highest similarity (56%) with that of Acinetobacter calcoaceticus ADP1 and lower similarity (36%) with a membrane-bound glucose dehydrogenase of Escherichia coli. The function of the gene coding for QDH was confirmed by heterologous gene expression in pyrroloquinoline quinone-synthesizing Pseudomonas putida HK5.     

Evolution of rosmarinic acid biosynthesis

Rosmarinic acid and chlorogenic acid are caffeic acid esters widely found in the plant kingdom and presumably accumulated as defense compounds. In a survey, more than 240 plant species have been screened for the presence of rosmarinic and chlorogenic acids. Several rosmarinic acid-containing species have been detected. The rosmarinic acid accumulation in species of the Marantaceae has not been known before. Rosmarinic acid is found in hornworts, in the fern family Blechnaceae and in species of several orders of mono- and dicotyledonous angiosperms. The biosyntheses of caffeoylshikimate, chlorogenic acid and rosmarinic acid use 4-coumaroyl-CoA from the general phenylpropanoid pathway as hydroxycinnamoyl donor. The hydroxycinnamoyl acceptor substrate comes from the shikimate pathway: shikimic acid, quinic acid and hydroxyphenyllactic acid derived from l-tyrosine. Similar steps are involved in the biosyntheses of rosmarinic, chlorogenic and caffeoylshikimic acids: the transfer of the 4-coumaroyl moiety to an acceptor molecule by a hydroxycinnamoyltransferase from the BAHD acyltransferase family and the meta-hydroxylation of the 4-coumaroyl moiety in the ester by a cytochrome P450 monooxygenase from the CYP98A family. The hydroxycinnamoyltransferases as well as the meta-hydroxylases show high sequence similarities and thus seem to be closely related. The hydroxycinnamoyltransferase and CYP98A14 from Coleus blumei (Lamiaceae) are nevertheless specific for substrates involved in RA biosynthesis showing an evolutionary diversification in phenolic ester metabolism. Our current view is that only a few enzymes had to be “invented” for rosmarinic acid biosynthesis probably on the basis of genes needed for the formation of chlorogenic and caffeoylshikimic acid while further biosynthetic steps might have been recruited from phenylpropanoid metabolism, tocopherol/plastoquinone biosynthesis and photorespiration.     

Production of caffeic,chlorogenic and rosmarinic acids in plants and suspension cultures of Glechoma hederacea

Glechoma hederacea L. (Lamiaceae) is a perennial plant, which is distributed widely in Europe, Asia and America. Important anti-oxidant compounds are caffeic acid esters like rosmarinic acid (RA) and chlorogenic acid (CA). Phenylalanine ammonia-lyase (PAL) and rosmarinic acid synthase (RAS, 4-coumaroyl-CoA:hydroxyphenyllactic acid hydroxycinnamoyltransferase) contribute to the formation of RA. Our aim in this study was to follow the accumulation of RA, CA and caffeic acid in a suspension culture of G. hederacea. Growth, medium and secondary metabolism parameters were determined during a culture period of 14 days. The maximal PAL activity was observed on day 5 and the maximal RAS activity on day 8. The RA content was exceedingly high and reached 25.9% of the dry mass on day 7. Caffeic acid and CA contents remained rather low. Furthermore, the presence of RA, CA and caffeic acid and the expression patterns of RAS and hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (HST), an important enzyme of monolignol formation, in leaves, flowers, stems and roots of naturally grown G. hederacea were assessed. The expression of RAS and HST genes was detectable in all organs except roots. Flowers accumulated 12.5% RA in their dry mass, leaves, stems and roots about 1%. CA was highest in leaves (2.0%), while it was at 1.6% in flowers, 1.3% in stems and almost undetectable in roots. The caffeic acid content remained at or below 0.4% of the dry weight in all organs.     

Anionic derivatives of xyloglucan function as acceptor but not donor substrates for xyloglucan endotransglucosylase activity

Tamarind xyloglucan was oxidised by reaction with sodium hypochlorite in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO). Galactose residues and non-xylosylated glucose residues were thus converted into galacturonic and glucuronic acid residues, respectively, producing an anionic polysaccharide. Acid hydrolysis of oxidised xyloglucan yielded two aldobiouronic acids, deduced to be β-d-GalpA-(1→2)-d-Xyl and β-d-GlcpA-(1→4)-d-Glc. Anionic xyloglucan had a decreased ability to hydrogen-bond to cellulose and to complex with iodine. It was almost totally resistant to digestion by cellulase [endo-(1→4)-β-glucanase] and did not serve as a donor substrate for xyloglucan endotransglucosylase (XET) activity. Like several other anionic polysaccharides, it promoted XET activity when unmodified (non-ionic) xyloglucan was used as donor substrate. Anionic xyloglucan may mimic polyanions whose presence in the plant cell wall promotes the action of endogenous XTH proteins. NaOCl with TEMPO oxidised the heptasaccharide, XXXG, to form XXX-glucarate, which did serve as an acceptor substrate although at a rate approximately fourfold less than XXXG itself. Anionic derivatives of xyloglucan, acting as acceptor but not donor substrates, may be valuable tools for exploring the biological roles of XTHs in the integration versus the re-structuring of xyloglucan in the plant cell wall.     

α-Chymotrypsin-Catalyzed Peptide Synthesis Using <Emphasis Type="Italic">N</Emphasis>-Protected <Emphasis Type="SmallCaps">D</Emphasis>-Amino Acid Carbamoylmethyl Esters as Acyl Donors

α-Chymotrypsin-catalyzed peptide synthesis was carried out between an N-protected D-amino acid ester and an L-amino acid amide (acyl donor, 10 mM; acyl acceptor, 50 mM; enzyme, 2 mg ml⁻¹; pH 8). By using a highly reactive carbamoylmethyl (Cam) ester as acyl donor, the D-amino acid was incorporated into the N-terminus of the resulting dipeptide amide. N-Protected dipeptide amides bearing D-amino acids such as D-Phe, D-Leu and D-Ala at their N-terminus were synthesized in high yields (up to 80%) in 1–3 h.